I have a quick question. When you prep a god there is a chance that the god will spawn behind some walls that are still technically speaking a few tiles from the player, but are unreachable unless you kill the monsters on the path or carve a path with endiswal. Shouldn't the altar just spawn in the "lobby" since that is the purpose of the prep?

Labyrinth and Ick Swamp are particularly bad for altar preps. Half of the reason to prep a god is to begin worship immediately, so if the god is cut off from your start position then it defeats the whole point of the prep. This is especially egregious with Jehora Jeheyu, where every single tile you explore before beginning worship reduces his usefulness.